Pre3 problem.

[pre65]

My Pre3 has a problem.

I have a noise on one channel, it's regular, but intermittent. I say intermittent but the gaps between are very small. A bit like motorboating but not.

When the noise appears (seems to need a little while to start) the volume control (shunted alps) and selector switch have no effect, even mute.

I did change the two 0.1uf coupling caps but that made no difference.

Help.

[Richard]

Hi Philip,

Sounds like a noisy valve, have you swapped them over to check or popped in a new one?

Pre3 runs them quite hard compared with a lot of other gear (several whole mA!) and Gerry B and I have both had noisy ECC82, the supplied JJs in particular.

I think they would be fine in gentler applications but perhaps the extra heat gets to them. We made up a good pair between ours and that was fine and I use some nos Mazda/Thorn which are good and have been in 2 or 3 years now

[pre65]

I did try swapping the two valves around but the noise stayed put.

I'll see if I can find the original valves and try them again.

[pre65]

I found the two ECC82 and plugged them in, and the noisy channel was noisy as soon as I switched on.

I wiggled the valve a bit and it's gone quiet for now. Will see how it responds after 30 mins or so.

I was using GE 5814wa up till today.

[pre65]

Touch wood ( puts finger on bonce ) the pre3 is still noise free.

[Richard]

Great stuff, what do you think it was, noisy valve, dusty socket, or is it worth resoldering the bases to the pcb do you reckon?